Adjust modem volume to more closely match system volume

This patch increases the volume from calls (incoming volume, so from the person calling you) by 50% to bring the call volume to be similar to that of what you get from the system volume.

This attempts to fix #58 (closed). Helps with issue #56 due to making the volume of the notifications less loud in comparison with the call audio.

This is tested using the BM818-A1 modem, before merging we should get this tested with each modem type. I don't know if the device name is the same across all the modems, and also don't know if the volume difference is the same across all the modem types.

• BM818-A1
• BM818-E1
• BM818-T1

Testing: Tested both speakerphone and non speakerphone.

• I did need to reduce the volume from 100% to 70% on the non-speakerphone speaker as it was a little too loud.
• The testing I did compared a youtube video to me speaking (separately so there was no ducking) attempting to make them about the same audio level (this is where the 50% increase came from).
• Testing was only done by testing by ear, no precise volume measurements were done.

From a usability standpoint, this could have the following issues:

• If a user has already adjusted the modem volume, this will override their change. (I don't see a way around this)
• As the user may be use to running with the differing volume level of calls, an update with this may require them to readjust system volume. (I don't see a way around this either)